Thank you for your post. I absolutely agree with your percentages. I just helped with a tricky tray for an animal shelter, and out of 665 emails/on-line forms, I received 61 donations. There was another woman who went door to door for the local places I couldn't come up with email addresses for. I don't know what her success rate was. It does get discouraging.
But every email I get that says no, I replay with "thank you for your consideration and for taking the time to reply". I'd rather have a no than nothing/waiting/hoping for a reply. So I want them to know that. There is nothing magic about any of this. It takes a lot of work.
Please don't get to discouraged about no's. My typical expectations for receiving donations from companies is 15% to 20% for local businesses, 10% for businesses in your state, and 5% for national corporations. There are just so many non profits that are asking for donations that they can't give to everyone. That said, I find email and the "contact us" section to be very useful. This allows you to send out a lot of requests from your home without costing any money. If you send out 20 requests a day and you get a donation from 10 percent of these emails, you would get about 30 donations a month. Check out the advertisements you get in the mail, yelp, groupon, and living social for your area. Also google "fun things to do in (your state or closest city)" Usually there will be numerous websites that list attractions, museums, restaurants, and other services.
We had a lawyer donate a gift certificate towards services last year. It didn't go well but it is good to think outside the box. You never know what people might like or catch their eye. Usually the more popular items are museum passes, restaurant gift certificates, gift baskets, wine, yoga gift cards.
For advertising, contact your local news outlets, send press releases to radio stations, newspapers, Etc. Many websites have event calendars online. You can submit your event details for free. We have "themed" events that appeal to the public.